Thrust reversing apparatus

ABSTRACT

Jet engine includes elongate streamlined shroud and a central body located substantially coaxially within at least the aft portion of the shroud to define between them a generally annular duct for rearward flow of a propulsion gas stream. The shroud may be the casing surrounding the engine, and the central body may be the &#39;&#39;&#39;&#39;bullet&#39;&#39;&#39;&#39; or center body aft of the turbine to define the profile of the discharge throat. In a fan type engine, the central body is the casing for the engine itself and the shroud is radially spaced from the casing to form a fan air duct. The reverser includes peripherally arranged outflow passage means extending through shroud wall forward of its trailing edge. A plurality of sets of control doors are peripherally arranged in the passage means and each set includes a blocker door and a deflector door. In preferred form, each blocker door is pivoted forward of its aft end to the shroud to swing in and contact central body, and each deflector door is pivoted at its aft end to the aft end of the blocker door to be bodily displaced and to swing outwardly. An operating lever is pivotally connected at its forward end to the shroud and at its aft end to a point intermediate the forward and aft end of the deflector door to complete a four bar linkage in which the doors themselves serve as two of the links. The operating lever is formed as a bell crank which is actuated by a servo motor.

Uite States atent Wright 0ct.9,i973

[ THRUST REVERSING APPARATUS [75] Inventor: 'Wallace Wright, San Diego,Calif.

[73] Assignee: Rohr Industries, Inc., Chula Vista,

Calif.

22 Filed: Feb. 24, 1972 21 Appl.No.: 229,046

Primary Examiner-George E. A. l-lalvosa Assistant Exam inerS. D.Basinger Att0mey-George E. Pearson [57] ABSTRACT Jet engine includeselongate streamlined shroud and a central body located substantiallycoaxially within at least the aft portion of the shroud to definebetween them a generally annular duct for rearward flow of a propulsiongas stream. The shroud may be the casing surrounding the engine, and thecentral body may be the bullet or center body aft of the turbine todefine the profile of the discharge throat. In a fan type engine, thecentral body is the casing for the engine itself and the shroud isradially spaced from the casing to form a fan air duct. The reverserincludes peripherally arranged outflow passage means extending throughshroud wall forward of its trailing edge. A plurality of sets of controldoors are peripherally arranged in the passage means and each setincludes a blocker door and a deflector door. In preferred form, eachblocker door is pivoted forward of its aft end to the shroud to swing inand contact central body, and each deflector door is pivoted at its aftend to the aft end of the blocker door to be bodily displaced and toswing outwardly. An operating lever is pivotally connected at itsforward end to the shroud and at its aft end to a point intermediate theforward and aft end of. the deflector door to complete a four barlinkage in which the doors themselves serve as two of the links. Theoperating lever is formed as a bell crank which is actuated by a servomotor.

5 Claims, 4 Drawing Figures Patented Oct. 9, 1973 2 Sheets-Sheet 1Patented Oct. 9, 1973 2 Sheets-Sheet B THRUST REVERSING APPARATUSBACKGROUND OF THE INVENTION This invention lies in the field of gasturbine engines, commonlycalled jet engines, which produce reactionthrust by rearward ejection of a high velocity gas stream. In aconventional jet engine, the gas stream consists entirely of the exhaustfrom the turbine exhaust but a large proportion is air driven rearwardby an enlarged axial flow compressor through an annular duct between theengine casing and a surrounding shroud.

Airplanes equipped with jet type engines develop very high air speedsand have correspondingly high landing speeds which place a heavy burdenon the wheel brakes. To reduce this burden, most such airplanes areprovided with means to reverse the direction of flow of the jet streamduring landing runs to produce a reverse thrust. Many different types ofthrust reversers have been developed and used for this purpose. All ofthem utilize a basic principle of blocking rearward flow of the jetstream and diverting it laterally and forwardly. One type uses blockerdoors swung directly behind the exhaust jet nozzle and divergingforwardly. Another type uses openings in the side walls of the nozzle ora surrounding fan air shroud together with blocker doors which swingtoward the engine axis to block rearward flow and extend outward todirect the diverted flow laterally and forwardly. Still another typeSUMMARY OF THE INVENTION The present invention obtains the benefitsmentioned above while providing an apparatus which adds very littleweight or complexity, with relatively few machined parts, thus reducinginitial cost as well as maintenance expense.

Generally stated, in presently preferred form, the apparatus includes anelongate streamlined shroud and a central body located substantiallycoaxially within at least the aft portion of the shroud. In the case ofa conventional jet engine, the shroud may be the engine casing itselfsurrounding the engine and nozzle and defining a gas discharge passage,and the central body may be a bullet or center body aft of the turbine.In the case of a fan type engine, the central body is the casing aroundthe engine and the shroud is radially spaced from the casing to form afan air duct. Peripherally arranged outflow passage means is provided ashort distance forward of the trailing edge of the shroud and extendsthrough the inner and outer walls. The passage means may compriseseveral discrete passages or a single substantially continuous passagewith spaced axially extending support structures connecting the aftsection of the shroud to the main body.

In either type of passage means there are a plurality of peripherallyadjacent sets of control doors located in the passage means when stowedand extending angularly inward and outward when deployed. Each setcomprises a blocker door and a deflector door. In the preferred form theblocker door is pivotally mounted forward of its aft end of the shroudand, in deploying,

the forward portion swings inward toward the central body while the aft,shorter, portion swings outward. The deflector door is pivotallyconnected at its aft end to the aft end of the blocker door and, indeploying, it swings outward and is also bodily displaced outward by themovement of the blocker door. An operating lever is pivotally connectedat its forward end to the shroud and at its aft end to a pointintermediate between the forward and aft ends of the deflector door tocomplete a four bar linkage in which the doors themselves serve as twoof the links.

Actuating means are attached to the linkage to cause the doors to movebetween stowed and deployed position. These means include bell crankarms connected to the operating levers and pivot shafts which may beuniversally connected end to end around the circumference to cause allof the sets of doors to move in unison. Power is supplied by servomotors connected to at least some of the bell crank arms on theoperating levers.

BRIEF DESCRIPTION OF THE DRAWINGS Various other advantages and featuresof novelty willbecome apparent'as the description proceeds inconjunction with the accompanying drawings, in which:

FIG. 1 is a schematic view in side elevation of a fan DESCRIPTION OFPREFERRED EMBODIMENTS The apparatus of this invention is generallyschematically illustrated in FIG. 1, in which the engine 10 is encasedwithin a core cowl or central body 12 which terminates rearwardly at thenozzle exit 14. At its forwardend, the engine is provided with an axialflow compressor or fan 16, the radially inner portion 18 of whichdirects combustion air into central body 12 and the radially outerportion 20 of which drives a jet or fan air stream rearward outside ofthe central body to directly produce jet thrust. Surrounding the fanandengine, and' substantially coaxial therewith, is an elongategenerally annular streamlined shroud 22 having radially spaced inner andouter walls 24 and 26. The shroud is mountedv on wing 30 by means ofstrut 32. The inner wall 24 is radially spaced from center body 12 toform an annular duct 28 for rearward flow of the fan air stream. While aforward fan type is shown, the apparatus is applicable to an aft fantype in the same way.

FIG. 2 is a similar illustration of a conventional jet engine assemblyin which engine 34, having an exhaustv exit plane 36, is encased withina shroud 38 having inner and outer walls 40 and 42. The shroud extendsaft of the engine proper to define an exhaust gas passage 44 to receiveand control the turbine exhaust. A bullet" or center body constitutes acentral body 46 substantially coaxial with and extending into at leastthe aft portion of the shroud to a position aft of the turbine exitplane to define with inner wall 40 the profile of the passage 44. Theshroud is mounted on wing 30. by means of strut 32.

It will be seen that in both cases a construction is provided in which ashroud surrounds a central body which is substantially coaxial with andextends into at least the aft portion of the shroud to define betweenthem a generally annular duct for the rearward flow of a propulsion gasstream. Thus, the invention may be applied to either form of engine inexactly the same way. Each shroud is provided forward of its trailingedge 48 or 50 with peripherally arranged outflow passage means 52extending through the inner and outer walls, and each passage means isprovided .with sets of control doors, the outer ones being deflectordoors 54 and the inner ones being blocker doors 56. As indicatedschematically in FIGS. 1 and 2, when the doors are stowed they block thepassage means 52 but do not obstruct ducts 28 or 44. When they aredeployed to the broken line positions, doors 56 form rearwardlydivergent frustocones to block rearward flow through the ducts anddivert the gases outward, and doors 54 form forwardly divergentfrusto-cones to give the outflow a forward component and produce reversethrust.

The detailed construction of the apparatus is illustrated in FIG. 3 onan enlarged scale using the reference characters of FIG. 1, although itis to be noted that it applies in the same way to FIG. 2.

As previously mentioned, passage means 52 may be a substantiallyuninterrupted passage extending through walls 24 and 26 with a minimumamount of support structure extending between aft portion 58 and mainbody 60 or it amy comprise a series of peripherally spaced discretepassages with shroud structure extending between them and defining skinportions of inner and outer walls 24 and 26. In either case a pluralityof sets of control doors are arranged in lateral adjacency around theperiphery of the shroud in the passage means, each set comprising ablocker door 56 and a deflector door 54.

Blocker door 56 is pivotally mounted to the shroud on a transverse axisat point 62, the major portion 64 being forward of the pivot and theminor portion 66 being aft of the pivot. When the door is deployed fromits broken line position flush with the inner wall of the shroud to itssolid line position the leading edge 68 contacts the central body andthe trailing edge 70 swings out beyond the contour of the shroud, andthe assemblage of all of the blocker doors forms a rearwardly divergentfrusto-cone which diverts the propulsion gas stream smoothly andgradually outward to the passage means which has been opened by thedeployment of the doors.

Deflector door 54 is pivotally connected at its aft end or trailing edge72 to the trailing edge 70 of door 56 by pivot pin 74 having atransverse axis. An operating lever 76 is pivotally connected at itsforward end 78 to the shroud adjacent to the forward margin of thepassage means by a pivot pin 80 having a transverse axis, and its aftend 82 is pivotally connected to door 54 by pivot pin 84 at a selectedpoint intermediate between leading edge 86 and trailing edge 72 of thedoor. This completes a four bar linkage consisting of stationary shroudstructure, the operating lever, and the aft portions of the two doors.

Operating lever 76 is actually the first arm of a bell crank 88 whichhas a second arm 90 extending at an angle to the first arm. Theactuating means for the doors comprises arm 90 and pivot pin 80, whichmay be an elongate shaft universally connected at its ends to similarpivot shafts for the adjacent sets of doors, and all of the pivot shaftsaround the periphery may be joined in the same way to cause them torotate in unison. A servo motor 92 has a cylinder 94 connected to theshroud structure, piston not shown, and a piston rod 96 pivotallyconnected to the free end of arm to move the latter and operating lever76 between stowed and deployed positions. If pivot shafts 80 are used tosynchronize movement they are fixedly connected to the bell cranks.

It will be seen that the servo motor actuates the four bar linkage. Whenoperating lever 76 swings to deployed position it swings door 54outward, pulling door 56 inward. Since door 54 is pivotally carried bythe trailing edge of door 56, it is also bodily displaced outward to theposition shown in solid lines. The assemblage of all of the doors 54swinging outward forms a forwardly divergent frusto-cone which furtherdeflects the exiting jet stream and gives it a forward component toproduce reverse thrust.

The arrangement illustrated in FIG. 3 may be readily modified by asimple reversal in which door 54 would be pivotally mounted on theshroud and door 56 would be displacably carried by door 54. Theactuating mechanism would, of course, also be reversed with operatingarm 76 connected to door 56. However, the arrangement shown is preferredbecause it is desirable to shift the deflector door assemblage as farout as possible and attain a more complete reversal of the flow path.

There are substantial areas of each door of a set aft of theirsupporting hinge points, and the closing pressure of the gas outflow onthese areas largely balances the opening pressure on the areas of theforward portions so that relatively low operating forces are required.To achieve a close balance, the respective areas may be tailored withinthe limits of the primary functions of the doors.

A servo motor and separate actuating linkage may be provided for eachset of doors or for a pair or group of sets, or all ofthe pivot shafts80 may be connected end to end around the periphery as previouslymentioned, with an adequate number of servo motors connected to selectedbell cranks.

When passage means 52 is formed as a substantially continuous passagewith doors 54 and 56 immediately adjacent to each other, the fore andaft margins of peripherally adjacent doors separate as the doors deploy.Since the resulting open gaps would reduce the effectiveness of theapparatus, the doors are provided with slidably overlapping portionswhich maintain a substantial seal between the doors at all times. Asshown in FIG. 4, each door 54 is provided with step-cut side marginalportions 98 and 100 arranged in overlying relation, each portion havinga sufficient peripheral extent to preserve the seal when the doors arefully deployed. Doors 56 are provided with similar step-cut sidemarginal portions because these doors also separate and approach eachother during operation.

It will be apparent that the invention described above providesapparatus which performs the desired thrust reversing function veryeffectively and with a minimum number of components arranted to requirerelatively low operating power, the construction being simple and ruggedfor low first cost and maintenance expense.

I claim:

1. Thrust reversing apparatus for use in combination with a jet engineproducing a rearwardly directed propulsion gas stream, comprising: anelongated streamlined shroud having inner and outer walls spaced fromeach other and a central body located substantially coaxially within atleast the aft portion of the shroud; the inner wall of the shroud beingradially spaced outward from the central body to define therewith agenerally annular duct for rearward flow of the propulsion gas stream;peripherally arranged outflow passage means extending through the innerand outer walls of the shroud forward of its trailing edge for lateraloutward flow of the propulsion gas stream during reverse thrustoperation; and a plurality of sets of flow control doors arranged inlateral adjacency around the periphery of the shroud in the passagemeans; each set including a blocker door and a deflector door; a firstdoor of each set being pivotally mounted on the shroud at a pointforward of the aft end of the door on a transverse pivotal axis to swingbetween stowed position closing a portion of the passage means at afirst wall of the shroud and deployed position with its forward portionextending forward of the pivot at a substantial angle to thelongitudinal axis of the shroud and with its aft portion extending aftof the pivot at a substantial opposite angle to the longitudinal axis ofthe shroud; a second door of each set being pivotally connected at itsaft end to the aft end of the first door of the set on a transversepivotal axis to swing between stowed position closing a portion of thepassage means at the second wall of the shroud and deployed positionlaterally displaced and extending forward at a substantial angle to thelongitudinal axis of the shroud and opposite to the angular displacementof the forward portion of the first door; and operating lever pivotallyconnected at its first end to the shroud and pivotally connected at itssecond end to a point intermediate the forward and aft ends of thesecond door to complete a four bar linkage consisting of the shroudstructure, the operating lever, and the aft portions of the two doors ofthe set; and actuator means 1 connected to the linkage to move the doorsbetween stowed and deployed positions; the actuator means for all of thesets being operable in unison to move all of the blocker doors todeployed position contacting the central body and defining a rearwardlydivergent frusto-cone to divert the propulsion gas stream smoothly andgradually outward to the passage means, and to move all of the deflectordoors to deployed position defining a forwardly divergent frusto-cone tofurther deflect the exiting stream outward with a forward flow componentto produce a reverse thrust said first door of each set being a blockerdoor, and the second door of each set being a deflector door. v

2. Apparatus as claimed in claim I; the first end of the operating leverbeing forward of its second end and being pivotally connected to theshroud adjacent to the forward margin of the passage means.

3. Apparatus as claimed in claim 1; the actuating means being connectedto the operating levers of the several sets of control doors.

4. Apparatus as claimed in claim 3; including a plurality ofcircumferentially spaced bell cranks having first and second armsextending at an angle to each other away from a common pivot; the firstarm of each bell crank being the operating lever of one of the four barlinkages; and a servo motor mounted on the shroud and operativelyconnected to the second arm of each bell crank.

5. Apparatus as claimed in claim 1; in which the shroud is a casingsurrounding the engine and nozzle and defining a rearwardly dischargingturbine gas passage; and the central body is a gas deflecting centerbody located aft of the turbine exit plane to cooperate with the shroudin defining the profile of the discharge duct.

1. Thrust reversing apparatus for use in combination with a jet engineproducing a rearwardly directed propulsion gas stream, comprising: anelongated streamlined shroud having inner and outer walls spaced fromeach other and a central body located substantially coaxially within atleast the aft portion of the shroud; the inner wall of the shroud beingradially spaced outward from the central body to define therewith agenerally annular duct for rearward flow of the propulsion gas stream;peripherally arranged outflow passage means extending through the innerand outer walls of the shroud forward of its trailing edge for lateraloutward flow of the propulsion gas stream during reverse thrustoperatioN; and a plurality of sets of flow control doors arranged inlateral adjacency around the periphery of the shroud in the passagemeans; each set including a blocker door and a deflector door; a firstdoor of each set being pivotally mounted on the shroud at a pointforward of the aft end of the door on a transverse pivotal axis to swingbetween stowed position closing a portion of the passage means at afirst wall of the shroud and deployed position with its forward portionextending forward of the pivot at a substantial angle to thelongitudinal axis of the shroud and with its aft portion extending aftof the pivot at a substantial opposite angle to the longitudinal axis ofthe shroud; a second door of each set being pivotally connected at itsaft end to the aft end of the first door of the set on a transversepivotal axis to swing between stowed position closing a portion of thepassage means at the second wall of the shroud and deployed positionlaterally displaced and extending forward at a substantial angle to thelongitudinal axis of the shroud and opposite to the angular displacementof the forward portion of the first door; and operating lever pivotallyconnected at its first end to the shroud and pivotally connected at itssecond end to a point intermediate the forward and aft ends of thesecond door to complete a four bar linkage consisting of the shroudstructure, the operating lever, and the aft portions of the two doors ofthe set; and actuator means connected to the linkage to move the doorsbetween stowed and deployed positions; the actuator means for all of thesets being operable in unison to move all of the blocker doors todeployed position contacting the central body and defining a rearwardlydivergent frusto-cone to divert the propulsion gas stream smoothly andgradually outward to the passage means, and to move all of the deflectordoors to deployed position defining a forwardly divergent frusto-cone tofurther deflect the exiting stream outward with a forward flow componentto produce a reverse thrust said first door of each set being a blockerdoor, and the second door of each set being a deflector door. 2.Apparatus as claimed in claim 1; the first end of the operating leverbeing forward of its second end and being pivotally connected to theshroud adjacent to the forward margin of the passage means.
 3. Apparatusas claimed in claim 1; the actuating means being connected to theoperating levers of the several sets of control doors.
 4. Apparatus asclaimed in claim 3; including a plurality of circumferentially spacedbell cranks having first and second arms extending at an angle to eachother away from a common pivot; the first arm of each bell crank beingthe operating lever of one of the four bar linkages; and a servo motormounted on the shroud and operatively connected to the second arm ofeach bell crank.
 5. Apparatus as claimed in claim 1; in which the shroudis a casing surrounding the engine and nozzle and defining a rearwardlydischarging turbine gas passage; and the central body is a gasdeflecting center body located aft of the turbine exit plane tocooperate with the shroud in defining the profile of the discharge duct.